Objective:To outline the procedure of polysomnography as carried out in a sleep disorders unit in Melbourne and to describe the patients undergoing polysomnography in terms of their age and sex and the sleep disorder diagnosed.Design:A retrospective survey of consecutive patients who required diagnostic polysomnography.Setting:The Sleep Disorders Unit at Epworth Hospital, a large private hospital in Melbourne.Patients:Two hundred consecutive patients who underwent polysomnography over a seven‐month period. Their ages ranged from 19 to 77 years.Interventions:All patients had diagnostic polysomnography for one night in the sleep laboratory. This involved 12 to 14 physiological variables being monitored continuously overnight by means of a new digital recording and sleep analysis system.Main outcome measures:Patients were categorised according to their main sleep disorder or primary diagnosis. Additional sleep disorders in some patients were categorised as secondary diagnoses.Results:The commonest age group among both male and female patients was 40–49 years. Overall, men outnumbered women three to one. Almost two‐thirds of all patients had as their primary diagnosis some degree of obstructive sleep apnoea syndrome or simple snoring. The next most common diagnosis was periodic limb movement disorder. The remaining diagnoses included a variety of sleep disorders, from narcolepsy to sleep terrors.Conclusions:Despite its complexity and time‐consuming nature, polysomnography is an essential procedure for the diagnosis and treatment of a wide range of sleep disorders. More sleep laboratories and a greater emphasis on the multidisciplinary teaching of sleep disorders medicine will be required in Australia.